The Hazard Assessment in Representative Onshore Oil Wells for Improve the Process Safety

In Brazil the approval of the Technical Regulation of the Oil Well Integrity Management System by the Brazilian National Oil and Gas Agency in 2016 which, among several management practices, established regulatory criteria for risk analysis containing requirements that must be applied to all Oil wells that cross reservoirs containing hydrocarbons, brought about the need to carry out thousands of analyzes considering the number of wells existing in the country. The establishment of criteria for grouping Oil wells into representative analyzes of sets of wells aims to severely reduce the work involved in issuing risk analyses, as well as maintaining an updated register of these risk analyzes for each phase of the well for operators. This paper proposes the use of preliminary risk analysis for Oil wells with common characteristics for representative association of a set of wells, which is named by "preliminary oil well-type risk analysis” and presents a reference model for wells with features defined in the presented model.

The Well-type Risk Analysis consists of the following steps:
a) Definition of the representative oil well-type;
b) Application of the risk analysis tecnique;
c) Association of oil wells with risk analaysis results;
d) Management of recommendations, changes and periodic reviews.

When characterizing the standard wells, the similarities between the wells that make up the set are considered, considering at least the following criteria:
1) Well environment (onshore or offshore) (note: in this paper, only onshore oil wells will be addressed);
2) Lifting method;
3) Completion scheme or CSB scheme (Solidarity Set of Barriers - is a set of one or more elements with the objective of preventing the unintentional flow of fluids from the formation to the external environment and between intervals in the well, considering all paths possible;
4) Availability of DHSV (Down Hole Safety Valve - Subsurface Safety Valve);
5) Mode of operation (the well is producer, injector or both);
6) Operating status: a. Perforated but not interlocked; b. In normal operation (including stopped wells), c. Out of operation (“hibernated”), d. Disabled (destined for abandonment);
7) Fluid characteristics: a. Operating fluid: gas, gas condensate, oil, produced water, steam; b. Contaminants: CO2, H2S, BSW (Basic Sediment and Water - is the fraction of fluids extracted from the oil well that are not hydrocarbons; expressed in volumetric percentage);
8) Surge - is a characteristic of the well that indicates that the reservoir open to the flow has sufficient pressure to raise the fluids contained within it to the surface (ground level). Note that every well equipped with a natural elevation method is a rising well, but not every emerging well can be equipped with a natural elevation method, as there may not be enough pressure to flow to the processing facility (despite there being pressure to lift to the surface );
9) Proximity of the well to housing, places where people gather, roads or other industrial installations;
10) Presence of geological risks (floods, floods, erosion processes, collapsible or expansive soils, landslides and related processes, subsidence and soil collapse in karst areas, regions with reports of earthquakes of magnitude equal to or greater than 5.0 in Richter scale etc.).

The use of well-type risk analysis proved to be an appropriate method for evaluating the risks of operating wells producing hydrocarbons or fluid injectors, saving time in carrying out this task by eliminating the creation of repetitive plans while preventing a loss of evaluation quality. Even though they had to divide the wells analyzed into two subgroups, the team behind this paper concluded that the gain in carrying out another section of analysis within the study makes up for not having to carry out a new risk analysis.